Vanadia/titania catalysts in selective catalytic reduction of nitric oxide with ammonia

Abstract

Selective catalytic reduction (SCR) of nitric oxide with ammonia was investigated over both phases of titania (Anatase and Rutile). All catalysts were characterized using BET surface area measurement, X-ray diffraction, in-situ and ambient laser Raman spectroscopy, X-ray photoelectron spectroscopy, and scanning electron microscopy techniques. A steady-state plug-flow reactor was used to investigate the effect of support material and catalyst loading on the catalytic activity. The activity of the catalysts supported over both anatase and rutile phases was found to go through a maximum with increasing vanadia loading. The catalysts supported over the rutile phase appeared to be more active on a unit surface area basis. At low catalyst loading levels, laser Raman spectroscopy showed the presence of polymeric vanadia surface species which are likely to be the active sites for the nitric oxide reduction reaction. For catalysts supported over the rutile phase, the presence of crystalline vanadium pentoxide did not seem to affect the catalytic activity significantly.